1.
Eukaryote
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A eukaryote is any organism whose cells contain a nucleus and other organelles enclosed within membranes. Eukaryotes belong to the taxon Eukarya or Eukaryota, the presence of a nucleus gives eukaryotes their name, which comes from the Greek εὖ and κάρυον. Eukaryotic cells also contain other membrane-bound organelles such as mitochondria and the Golgi apparatus, in addition, plants and algae contain chloroplasts. Eukaryotic organisms may be unicellular or multicellular, only eukaryotes form multicellular organisms consisting of many kinds of tissue made up of different cell types. Eukaryotes can reproduce asexually through mitosis and sexually through meiosis and gamete fusion. In mitosis, one cell divides to produce two identical cells. In meiosis, DNA replication is followed by two rounds of division to produce four daughter cells each with half the number of chromosomes as the original parent cell. These act as sex cells resulting from genetic recombination during meiosis, the domain Eukaryota appears to be monophyletic, and so makes up one of the three domains of life. The two other domains, Bacteria and Archaea, are prokaryotes and have none of the above features, eukaryotes represent a tiny minority of all living things. However, due to their larger size, eukaryotes collective worldwide biomass is estimated at about equal to that of prokaryotes. Eukaryotes first developed approximately 1. 6–2.1 billion years ago, in 1905 and 1910, the Russian biologist Konstantin Mereschkowsky argued three things about the origin of nucleated cells. Firstly, plastids were reduced cyanobacteria in a symbiosis with a non-photosynthetic host, secondly, the host had earlier in evolution formed by symbiosis between an amoeba-like host and a bacteria-like cell that formed the nucleus. Thirdly, plants inherited photosynthesis from cyanobacteria, the split between the prokaryotes and eukaryotes was introduced in the 1960s. The concept of the eukaryote has been attributed to the French biologist Edouard Chatton, the terms prokaryote and eukaryote were more definitively reintroduced by the Canadian microbiologist Roger Stanier and the Dutch-American microbiologist C. B. van Niel in 1962. In his 1938 work Titres et Travaux Scientifiques, Chatton had proposed the two terms, calling the bacteria prokaryotes and organisms with nuclei in their cells eukaryotes. However he mentioned this in one paragraph, and the idea was effectively ignored until Chattons statement was rediscovered by Stanier. In 1967, Lynn Margulis provided microbiological evidence for endosymbiosis as the origin of chloroplasts and mitochondria in cells in her paper. In the 1970s, Carl Woese explored microbial phylogenetics, studying variations in 16S ribosomal RNA and this helped to uncover the origin of the eukaryotes and the symbiogenesis of two important eukaryote organelles, mitochondria and chloroplasts

2.
Unikont
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The taxonomic affinities of the members of this clade were originally described and proposed by Thomas Cavalier-Smith. It includes amoebozoa, opisthokonts, and possibly Apusozoa, the validity of this proposed taxonomy has yet to ruled upon by the Society of Protistologists. Further work by Cavalier-Smith has shown that Sulcozoa is paraphyletic, Apusozoa also appears to be paraphyetic. Varisulca has been redefined to include planomonads, Mantamonas and Collodictyon, a new taxon has been created - Glissodiscea - for the planomonads and Mantamonas. Again, the validity of this revised taxonomy awaits approval by the Society, Amoebozoa seems to be monophyletic with two major branches, Conosa and Lobosa. Conosa is divided into the aerobic infraphylum Semiconosia and secondarily anaerobic Archamoebae, Lobosa consists entirely of non-flagellated lobose amoebae and has been divided into two classes, Discosea, which have flattened cells, and Tubulinea, which has predominantly tube-shaped pseudopodia. The group includes eukaryotic cells that, for the most part, have a single emergent flagellum, the unikonts include opisthokonts and Amoebozoa. By contrast, other eukaryotic groups, which more often have two emergent flagella, are often referred to as bikonts. Bikonts include Archaeplastida, Excavata, Rhizaria, and Chromalveolata, the unikonts have a triple-gene fusion that is lacking in the bikonts. This must have involved a double fusion, a pair of events, supporting the shared ancestry of Opisthokonta. Cavalier-Smith originally proposed that unikonts ancestrally had a single flagellum and single basal body and this is unlikely, however, as flagellated opisthokonts, as well as some flagellated Amoebozoa, including Breviata, actually have two basal bodies, as in typical bikonts. This paired arrangement can also be seen in the organization of centrioles in animal cells. In spite of the name of the group, the ancestor of all unikonts was probably a cell with two basal bodies

3.
Opisthokont
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The opisthokonts, sometimes referred to as the Fungi/Metazoa group, are generally recognized as a monophyletic clade. One common characteristic of opisthokonts is that flagellate cells, such as the sperm of most animals and it is this feature that gives the group its name. In contrast, flagellate cells in other eukaryote groups propel themselves with one or more anterior flagella, in some opisthokont groups, including most of the fungi, flagellate cells have been lost. The close relationship between animals and fungi was suggested by Thomas Cavalier-Smith in 1987, who used the informal name opisthokonta, early phylogenies placed fungi near the plants and other groups that have mitochondria with flat cristae, but this character varies. Animals and fungi are more closely related to amoebas than they are to plants. Opisthokonts are divided into Holomycota or Nucletmycea and Holozoa, no opisthokonts basal to the Holomycota/Holozoa split have yet been identified, however, a 2013 study suggests that there may be many more unicellular opisthokonts than previously suspected. Holomycota and Holozoa are composed of the following groups, the choanoflagellates have a circular mitochondrial DNA genome with long intergenic regions. This is four times as large as animal mitochondrial genomes and contains twice as many protein genes, the ichthyosporeans have a two amino acid deletion in their elongation factor 1 α gene that is considered characteristic of fungi. The ichthyosl genome is >200 kilobase pairs in length and consists of several hundred linear chromosomes that share elaborate terminal-specific sequence patterns

4.
Holozoa
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Holozoa is a group of organisms that includes animals and their closest single-celled relatives, but excludes fungi. Holozoa is also an old name for the tunicate genus Distaplia, proterospongia is an example of a colonial choanoflagellate that may shed light on the origin of sponges. The affinities of the other single-celled holozoans only began to be recognized in the 1990s, a group of mostly parasitic species called Icthyosporea or Mesomycetozoea is sometimes grouped with other species in Mesomycetozoa. The amoeboid genera Ministeria and Capsaspora may be united in a group called Filasterea by the structure of their thread-like pseudopods, along with choanoflagellates, filastereans may be closely related to animals, and one analysis grouped them together as the clade Filozoa. The oldest fossils of holozoans are animals, which date back to the Ediacaran period, the most up to date cladogram is

5.
Filozoa
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The Filozoa are a monophyletic grouping within the Opisthokonta. They include animals and their nearest unicellular relatives, the most up to date cladogram is The ancestral opisthokont cell is assumed to have possessed slender filose projections or tentacles. In some opisthokonts these were lost and they are retained in Filozoa, where they are simple and non-tapering, with a rigid core of actin bundles

6.
Animal
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Animals are multicellular, eukaryotic organisms of the kingdom Animalia. The animal kingdom emerged as a clade within Apoikozoa as the group to the choanoflagellates. Animals are motile, meaning they can move spontaneously and independently at some point in their lives and their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later in their lives. All animals are heterotrophs, they must ingest other organisms or their products for sustenance, most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago. Animals can be divided broadly into vertebrates and invertebrates, vertebrates have a backbone or spine, and amount to less than five percent of all described animal species. They include fish, amphibians, reptiles, birds and mammals, the remaining animals are the invertebrates, which lack a backbone. These include molluscs, arthropods, annelids, nematodes, flatworms, cnidarians, ctenophores, the study of animals is called zoology. The word animal comes from the Latin animalis, meaning having breath, the biological definition of the word refers to all members of the kingdom Animalia, encompassing creatures as diverse as sponges, jellyfish, insects, and humans. Aristotle divided the world between animals and plants, and this was followed by Carl Linnaeus, in the first hierarchical classification. In Linnaeuss original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, in 1874, Ernst Haeckel divided the animal kingdom into two subkingdoms, Metazoa and Protozoa. The protozoa were later moved to the kingdom Protista, leaving only the metazoa, thus Metazoa is now considered a synonym of Animalia. Animals have several characteristics that set apart from other living things. Animals are eukaryotic and multicellular, which separates them from bacteria and they are heterotrophic, generally digesting food in an internal chamber, which separates them from plants and algae. They are also distinguished from plants, algae, and fungi by lacking cell walls. All animals are motile, if only at life stages. In most animals, embryos pass through a stage, which is a characteristic exclusive to animals. With a few exceptions, most notably the sponges and Placozoa and these include muscles, which are able to contract and control locomotion, and nerve tissues, which send and process signals

7.
Eumetazoa
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Eumetazoa is a clade comprising all major animal groups except sponges, placozoa, and several other extinct or obscure life forms, such as Iotuba and Thectardis. Characteristics of eumetazoans include true tissues organized into layers, the presence of neurons. The clade is usually held to contain at least Ctenophora, Cnidaria, whether mesozoans belong is in dispute. Ctenophora now appear basal eumetazoa, and placozoa also appear to have emerged in eumetazoa, Eumetazoa would then be a basal Metazoan clade as sister of Porifera. Some phylogenists have speculated the sponges and eumetazoans evolved separately from single-celled organisms, however, genetic studies and some morphological characteristics, like the common presence of choanocytes, support a common origin. When treated as a formal taxon Eumetazoa is typically ranked as a subkingdom, the name Metazoa has also been used to refer to this group, but more often refers to the Animalia as a whole. Many classification schemes do not include a subkingdom Eumetazoa, over the last decade, the work of developmental biologists and molecular phylogeneticists spawned new ideas about bilaterian relationships resulting in a paradigm shift. The current widely accepted hypothesis, based on data, divides Bilateria into the following four superphylums, Deuterostomia, Ecdysozoa, Lophotrochozoa. The last three groups are collectively known as Protostomia. However, many skeptics emphasize the pitfalls and inconsistencies associated with the new data, in his 2001 book Animal Evolution, Interrelationships of the Living Phyla, he maintains the traditional divisions of Protostomia and Deuterostomia. It has been suggested that one type of clock and one approach to interpretation of the fossil record both place the evolutionary origins of eumetazoa in the Ediacaran. However, the earliest eumetazoans may not have left an impact on the fossil record. Tree of Life web project, US National Science Foundation, invertebrates and the Origin of Animal Diversity Evers, Christine A. 2005 Metazoa, the Animals Nielsen, C.2001, Animal Evolution, Interrelationships of the Living Phyla, 2nd edition,563 pp. Oxford Univ. Manuel, M. Alivon, E. Boury-Esnault N. Vacelet, J. Le-Parco, journal of Evolutionary Biology 14, 171–179. Peterson, Kevin J. McPeek, Mark A. & Evans, tempo & mode of early animal evolution, inferences from rocks, Hox, & molecular clocks

8.
Bilateria
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In contrast, radially symmetrical animals like jellyfish have a topside and a downside, but no identifiable front or back. The bilateria are a group of animals, including the majority of phyla but not sponges, cnidarians, placozoans. For the most part, bilateral embryos are triploblastic, having three germ layers, endoderm, mesoderm, and ectoderm. Nearly all are symmetrical, or approximately so, the most notable exception is the echinoderms, which achieve near-radial symmetry as adults. Except for a few phyla, bilaterians have complete digestive tracts with a separate mouth, some bilaterians lack body cavities, while others display primary body cavities or secondary cavities. The hypothetical most recent common ancestor of all bilateria is termed the Urbilaterian, the nature of the first bilaterian is a matter of debate. The first evidence of bilateria in the record comes from trace fossils in Ediacaran sediments. Earlier fossils are controversial, the fossil Vernanimalcula may be the earliest known bilaterian, fossil embryos are known from around the time of Vernanimalcula, but none of these have bilaterian affinities. Burrows believed to have created by bilaterian life forms have been found in the Tacuarí Formation of Uruguay. There are two main superphyla of Bilateria, the deuterostomes include the echinoderms, hemichordates, chordates, and a few smaller phyla. The protostomes include most of the rest, such as arthropods, annelids, mollusks, flatworms, there are a number of differences, most notably in how the embryo develops. In particular, the first opening of the embryo becomes the mouth in protostomes, many taxonomists now recognize at least two more superphyla among the protostomes, Ecdysozoa and Lophotrochozoa. Within the latter, some researchers also recognize another superphylum, Platyzoa, the arrow worms have proven particularly difficult to classify, with some taxonomists placing them among the deuterostomes and others placing them among the protostomes. The two most recent studies to address the question of chaetognath origins support protostome affinities, a modern consensus phylogeny for Bilateria is shown below, although the position of certain clades are still controversial and the tree has changed considerably between 2000 and 2010. Nodes marked with * have received broad consensus, a prominent alternative tree is championed by Nielsen. Embryological origins of the mouth and anus Tree of Life web project — Bilateria University of California Museum of Paleontology — Systematics of the Metazoa

9.
Nephrozoa
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Nephrozoa is a major clade of bilaterians including deuterostomes and protostomes. It is the extant sister clade of Xenacoelomorpha, the majority of bilaterian animals are split into two groups, the protostomes and deuterostomes. It seems very likely that the 555 million year old Kimberella was a member of the protostomes, balavoine, G. Adoutte, A.1998, One or three Cambrian radiations. Economou, A. D. Telford, M. J.2008, Testing the new animal phylogeny, molecular phylogenetics and evolution,49, 23-31. Baguñà, J. Riutort, M.2002, The Nemertodermatida are basal bilaterians and not members of the Platyhelminthes

10.
Deuterostome
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Deuterostomes are any members of a superphylum of animals. It is a clade of Protostomia, with which it forms the Nephrozoa clade. Deuterostomes are also known as enterocoelomates because their coelom develops through enterocoely, the phylum Chaetognatha may belong here, but molecular studies have placed them in the protostomes more often. Extinct deuterostome groups may include the phylum Vetulicolia, echinodermata and Hemichordata form the clade Ambulacraria. In both deuterostomes and protostomes, a zygote first develops into a ball of cells, called a blastula. In deuterostomes, the early divisions occur parallel or perpendicular to the polar axis and this is called radial cleavage, and also occurs in certain protostomes, such as the lophophorates. Most deuterostomes display indeterminate cleavage, in which the fate of the cells in the developing embryo are not determined by the identity of the parent cell. Thus, if the first four cells are separated, each cell is capable of forming a small larva, and if a cell is removed from the blastula. In deuterostomes the mesoderm forms as evaginations of the gut that pinch off. Both the Hemichordata and Chordata have gill slits, and primitive fossil echinoderms also show signs of gill slits, a hollow nerve cord is found in all chordates, including tunicates. Some hemichordates also have a nerve cord. In the early stage, it looks like the hollow nerve cord of chordates. It could have resembled the small group of Cambrian urochordate deuterostomes named Vetulicolia, the defining characteristic of the deuterostome is the fact that the blastopore becomes the anus, whereas in protostomes the blastopore becomes the mouth. The deuterostome mouth develops at the end of the embryo from the blastopore. The majority of more complex than jellyfish and other Cnidarians are split into two groups, the protostomes and deuterostomes. It seems likely that the 555 million year old Kimberella was a member of the protostomes. e, during the later part of the Ediacaran Era. The oldest discovered proposed deuterostome is Saccorhytus coronarius, which lived approximately 540 million years ago, the researchers that made the discovery believe that the Saccorhytus is a common ancestor to all previously-known deuterostomes. Fossils of one major group, the echinoderms, are quite common from the start of Series 2 of the Cambrian,521 million years ago

11.
Chordate
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Chordates are deuterostomes, as during the embryo development stage the anus forms before the mouth. They are also bilaterally symmetric coelomates, in the case of vertebrate chordates, the notochord is usually replaced by a vertebral column during development, and they may have body plans organized via segmentation. There are also additional extinct taxa, the Vertebrata are sometimes considered as a subgroup of the clade Craniata, consisting of chordates with a skull, the Craniata and Tunicata compose the clade Olfactores. Of the more than 65,000 living species of chordates, the worlds largest and fastest animals, the blue whale and peregrine falcon respectively, are chordates, as are humans. Fossil chordates are known from at least as early as the Cambrian explosion, Hemichordata, which includes the acorn worms, has been presented as a fourth chordate subphylum, but it now is usually treated as a separate phylum. The Hemichordata, along with the Echinodermata, form the Ambulacraria, the Chordata and Ambulacraria form the superphylum Deuterostomia, composed of the deuterostomes. Attempts to work out the relationships of the chordates have produced several hypotheses. All of the earliest chordate fossils have found in the Early Cambrian Chengjiang fauna. Because the fossil record of early chordates is poor, only molecular phylogenetics offers a prospect of dating their emergence. However, the use of molecular phylogenetics for dating evolutionary transitions is controversial and it has also proved difficult to produce a detailed classification within the living chordates. Attempts to produce family trees shows that many of the traditional classes are paraphyletic. While this has been known since the 19th century, an insistence on only monophyletic taxa has resulted in vertebrate classification being in a state of flux. Although the name Chordata is attributed to William Bateson, it was already in prevalent use by 1880, ernst Haeckel described a taxon comprising tunicates, cephalochordates, and vertebrates in 1866. Though he used the German vernacular form, it is allowed under the ICZN code because of its subsequent latinization, among the vertebrate sub-group of chordates the notochord develops into the spine, and in wholly aquatic species this helps the animal to swim by flexing its tail. In fish and other vertebrates, this develops into the spinal cord, the pharynx is the part of the throat immediately behind the mouth. In fish, the slits are modified to form gills, a muscular tail that extends backwards behind the anus. This is a groove in the wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus and it also stores iodine, and may be a precursor of the vertebrate thyroid gland

12.
Craniate
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A craniate is a member of the Craniata, a proposed clade of chordate animals with a skull of hard bone or cartilage. Included in the clade are the vertebrates, and non-vertebrate chordates with skulls, living representatives are the Myxini, Hyperoartia, and the much more numerous Gnathostomata. The craniate head consists of a brain, sense organs, including eyes, in addition to distinct crania, craniates possess many derived characteristics, which have allowed for more complexity to follow. In general, craniates are much more active than tunicates and lancelets and, as a result, have greater metabolic demands, aquatic craniates have gill slits, which are connected to muscles and nerves that pump water through the slits, engaging in both feeding and gas exchange. Muscles line the canal, moving food through the canal. Craniates have cardiovascular systems that include a heart with two or more chambers, red cells, and oxygen transporting hemoglobin, as well as kidneys. Linnaeus used the terms Craniata and Vertebrata interchangeably to include lampreys, jawed fishes, hagfishes were classified as Vermes, possibly representing a transitional form between worms and fishes. Dumeril grouped hagfishes and lampreys in the taxon Cyclostomi, characterized by horny teeth borne on an apparatus, a large notochord as adults. Cyclostomes were regarded as either degenerate cartilaginous fishes or primitive vertebrates, cope coined the name Agnatha for a group that included the cyclostomes and a number of fossil groups in which jaws could not be observed. Vertebrates were subsequently divided into two major sister-groups, the Agnatha and the Gnathostomata, stensiö suggested that the two groups of living agnathans arose independently from different groups of fossil agnathans. e. On this basis Janvier proposed to use the names Vertebrata and Craniata as two distinct and nested taxa, the argument is that, if Cyclostomata is indeed monophyletic, Vertebrata would return to its old content and the name Craniata, being superfluous, would become a junior synonym. Lines show probable evolutionary relationships, including extinct taxa, which are denoted with a dagger, the positions of the Lancelet, Tunicate, and Craniata clades are as reported in the scientific journal Nature. Note that this cladogram, in showing the extant cyclostomes as paraphyletic, is contradicted by all recent molecular data. Extinct genera Haikouella and Haikouichthys Campbell, Neil A. Reece, cleveland P. Hickman, J. Roberts, L. S. Keen, S. L. Larson, A. & Eisenhour, D. J. Animal Diversity, Fourth Edition. CS1 maint, Uses authors parameter Cracraft, Joel, Donoghue, new York, Oxford University Press US. Delarbre, Christiane, Gallut, C, Barriel, V, Janvier, P, Gachelin, G, complete Mitochondrial DNA of the Hagfish, Eptatretus burgeri, The Comparative Analysis of Mitochondrial DNA Sequences Strongly Supports the Cyclostome Monophyly. Parker, T. J. Haswell, W. A

13.
Vertebrate
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Vertebrates /ˈvɜːrtᵻbrᵻts/ comprise all species of animals within the subphylum Vertebrata /-ɑː/. Vertebrates represent the majority of the phylum Chordata, with currently about 66,000 species described. Vertebrates include the fish and the jawed vertebrates, which include the cartilaginous fish. A bony fish known as the lobe-finned fishes is included with tetrapods, which are further divided into amphibians, reptiles, mammals. Extant vertebrates range in size from the frog species Paedophryne amauensis, at as little as 7.7 mm, to the blue whale, vertebrates make up less than five percent of all described animal species, the rest are invertebrates, which lack vertebral columns. The vertebrates traditionally include the hagfish, which do not have proper vertebrae due to their loss in evolution, though their closest living relatives, hagfish do, however, possess a cranium. For this reason, the vertebrate subphylum is sometimes referred to as Craniata when discussing morphology, molecular analysis since 1992 has suggested that hagfish are most closely related to lampreys, and so also are vertebrates in a monophyletic sense. Others consider them a group of vertebrates in the common taxon of craniata. The word origin of vertebrate derives from the Latin word vertebratus, the Proto-Indo-European language origins are still unclear. Vertebrate is derived from the vertebra, which refers to any of the bones or segments of the spinal column. All vertebrates are built along the basic body plan, a stiff rod running through the length of the animal, with a hollow tube of nervous tissue above it. In all vertebrates, the mouth is found at, or right below, the remaining part of the body continuing after the anus forms a tail with vertebrae and spinal cord, but no gut. However, a few vertebrates have secondarily lost this anatomy, retaining the notochord into adulthood, such as the sturgeon, jawed vertebrates are typified by paired appendages, but this trait is not required in order for an animal to be a vertebrate. All basal vertebrates breathe with gills, the gills are carried right behind the head, bordering the posterior margins of a series of openings from the pharynx to the exterior. Each gill is supported by a cartilagenous or bony gill arch, the bony fish have three pairs of arches, cartilaginous fish have five to seven pairs, while the primitive jawless fish have seven. The vertebrate ancestor no doubt had more arches than this, as some of their relatives have more than 50 pairs of gills. In amphibians and some primitive fishes, the larvae bear external gills. These are reduced in adulthood, their function taken over by the gills proper in fishes, some amphibians retain the external larval gills in adulthood, the complex internal gill system as seen in fish apparently being irrevocably lost very early in the evolution of tetrapods

14.
Gnathostomata
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Gnathostomata /ˌneɪθoʊstoʊˈmɑːtə/ are the jawed vertebrates. The term derives from Greek, γνάθος jaw + στόμα mouth, gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all living vertebrates. Another is an immune system that uses VJ recombination to create antigen recognition sites. It is now assumed that Gnathostomata evolved from ancestors that possessed a pair of both pectoral and pelvic fins. The Osteostraci are generally considered the taxon of Gnathostomata. The mouth could then grow bigger and wider, making it possible to capture larger prey and this close and open mechanism would, with time, become stronger and tougher, being transformed into real jaws. Newer research suggests that a branch of Placoderms was most likely the ancestor of present-day gnathostomes and it also indicates that spiny sharks and Chondrichthyes represent a single sister group to the bony fishes. Late Ordovician-aged microfossils of what have been identified as scales of either acanthodians or shark-like fishes, undeniably unambiguous gnathostome fossils, mostly of primitive acanthodians, begin appearing by the early Silurian, and become abundant by the start of the Devonian. Some classification systems have used the term Amphirhina and it is a sister group of the jawless craniates Agnatha. Tree of Life discussion of Gnathostomata The Gill Arches, Meckels Cartilage

15.
Teleostomi
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Teleostomi is an obsolete clade of jawed vertebrates that supposedly includes the tetrapods, bony fish, and the wholly extinct acanthodian fish. Key characters of this include an operculum and a single pair of respiratory openings. The teleostomes include all jawed vertebrates except the chondrichthyans and the extinct class Placodermi, recent studies indicate that Osteichthyes evolved from placoderms like Entelognathus, while acanthodians are more closely related to modern chondrichthyes. Teleostomi, therefore, is not a valid, natural clade, the clade Teleostomi should not be confused with the similar-sounding fish clade Teleostei. The origins of the teleostomes are obscure, living teleostomes constitute the clade Euteleostomi, which includes all osteichthyans and tetrapods. Even after the acanthodians perished at the end of the Permian, teleostomes have two major adaptations that relate to aquatic respiration. First, the early teleostomes probably had some type of operculum, however, the development of a single respiratory opening seems to have been an important step. The second adaptation, the teleostomes also developed a primitive lung with the ability to use atmospheric oxygen. This developed, in species, into the lung and the swim bladder. Acanthodians share with Actinopterygii the characteristic of three otoliths, the sagitta in the sacculus, the asteriscus in the lagena, and the lapillus in the utriculus, in dipnoans there are only two otoliths and in Latimeria there is only one. However, most of the above synapomorphies can ultimately be found in several chondrychthyian groups

16.
Tetrapod
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The superclass Tetrapoda contains the four-limbed vertebrates known as tetrapods, it includes living and extinct amphibians, reptiles and mammals, as well as earlier extinct groups. The first tetrapods appeared by the late Devonian,367, the first tetrapods were primarily aquatic. Their descendants drove most amphibians to extinction as they began to dominate, the amniotes include the tetrapods that further evolved for flight—such as birds from among the dinosaurs, and bats from among the mammals. The change from a plan for breathing and navigating in water to a body plan enabling the animal to move on land is one of the most profound evolutionary changes known. It is also becoming increasingly well-understood as a result of more transitional fossil finds, many tetrapods have returned to partially aquatic or fully aquatic lives throughout the history of the group. Tetrapods can be defined in cladistics as the nearest common ancestor of all living amphibians and all living amniotes, the group so defined is the crown group, or crown tetrapods. The term tetrapodomorph is used for the definition, any animal that is more closely related to living amphibians, reptiles, birds. The group so defined is known as the total group. Stegocephalia is a larger group equivalent to some uses of the word tetrapod. Batrachomorphs are all sharing a more recent common ancestry with living amphibians than with living amniotes. Reptiliomorphs are all sharing a more recent common ancestry with living amniotes than with living amphibians. Tetrapoda includes four classes, amphibians, reptiles, mammals, however, that diversification process was interrupted at least a few times by major biological crises, such as the Permian–Triassic extinction event, which at least affected amniotes. As biodiversity has grown, so has the number of niches that tetrapods have occupied, the first tetrapods were aquatic and fed primarily on fish. Today, the Earth supports a diversity of tetrapods that live in many habitats. Tetrapods evolved from early bony fishes, specifically from the branch of lobe-finned fishes. The first tetrapods probably evolved in the Emsian stage of the Early Devonian from Tetrapodomorph fish living in water environments. The very earliest tetrapods would have been similar to Acanthostega, with legs and lungs as well as gills. The earliest tetrapods inhabited saltwater, brackish-water, and freshwater environments and these traits were shared with many early lobed-finned fishes

17.
Batrachomorpha
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Batrachomorpha is a name traditionally given to recent and extinct amphibians that are more closely related to modern amphibians than they are to reptiles. It most often includes the extinct groups Temnospondyli and Lepospondyli, the first tetrapods were all amphibians in the generic sense that they laid their eggs in water. Batrachomorphs composed one branch of these early tetrapods, while the reptiliomorphs composed the other, modern amphibians are descended from one line of Batrachomorphs, while all other modern tetrapods are descended from the one branch of reptiliomorphs, the amniotes. Amniotes achieved dominance, while all other reptiliomorphs and most batrachomorphs have gone extinct, the name Batrachomorpha was coined by the Swedish palaeontologist Gunnar Säve-Söderbergh in 1934 to refer to ichthyostegids, temnospondyls, anthracosaurs, and the frogs. Säve-Söderbergh held the view that salamanders and caecilians are not related to the tetrapods, but had developed independently from a different group of lobe-finned fish. In this view amphibians would be a group, and Batrachomorpha was erected to form a natural group consisting of the true amphibians. The salamanders and the Lepospondyli was consigned to Urodelomorpha, friedrich von Huene adopted it as a superorder of his subclass Eutetrapoda and included the orders Stegocephalia. Erik Jarvik, who took over Säve-Söderberghs work and shared his view of the origin of salamanders, used the more informally. Jarviks classification is no longer followed, all living amphibians and their fossil relatives now being classified together in the group Lissamphibia, michael Benton adopted the term Batrachomorpha to include all living amphibians and extinct relatives more closely related to amphibians than to reptiles. The actual content of Batracomorpha as cladistically defined is therefore uncertain, in the appendix to Vertebrate Palaeontology, Benton has given Batrachomorpha the rank of Subclass in his 2001 edition and Class in the 2004 edition. Benton, M. J. Vertebrate Paleontology, 2nd Ed, blackwell Science Ltd 3rd ed. Aspects of vertebrate phylogeny. In, Current Problems of Lower Vertebrate Phylogeny, Nobel Symposium 4, pp. 497–527

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Amphibian
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Amphibians are ectothermic, tetrapod vertebrates of the class Amphibia. They inhabit a variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Thus amphibians typically start out as larvae living in water, the young generally undergo metamorphosis from larva with gills to an adult air-breathing form with lungs. Amphibians use their skin as a respiratory surface and some small terrestrial salamanders and frogs lack lungs. They are superficially similar to lizards but, along with mammals and birds, reptiles are amniotes, the earliest amphibians evolved in the Devonian period from sarcopterygian fish with lungs and bony-limbed fins, features that were helpful in adapting to dry land. They diversified and became dominant during the Carboniferous and Permian periods, over time, amphibians shrank in size and decreased in diversity, leaving only the modern subclass Lissamphibia. The three modern orders of amphibians are Anura, Urodela, and Apoda, the number of known amphibian species is approximately 7,000, of which nearly 90% are frogs. The smallest amphibian in the world is a frog from New Guinea with a length of just 7.7 mm. The largest living amphibian is the 1.8 m Chinese giant salamander, the study of amphibians is called batrachology, while the study of both reptiles and amphibians is called herpetology. The word amphibian is derived from the Ancient Greek term ἀμφίβιος, the term was initially used as a general adjective for animals that could live on land or in water, including seals and otters. Traditionally, the class Amphibia includes all tetrapod vertebrates that are not amniotes, the numbers of species cited above follows Frost and the total number of known amphibian species is over 7,000, of which nearly 90% are frogs. With the phylogenetic classification, the taxon Labyrinthodontia has been discarded as it is a group without unique defining features apart from shared primitive characteristics. Classification varies according to the phylogeny of the author and whether they use a stem-based or a node-based classification. The phylogeny of Paleozoic amphibians is uncertain, and Lissamphibia may possibly fall within groups, like the Temnospondyli or the Lepospondyli. If the common ancestor of amphibians and amniotes is included in Amphibia, all modern amphibians are included in the subclass Lissamphibia, which is usually considered a clade, a group of species that have evolved from a common ancestor. The three modern orders are Anura, Caudata, and Gymnophiona, although the fossils of several older proto-frogs with primitive characteristics are known, the oldest true frog is Prosalirus bitis, from the Early Jurassic Kayenta Formation of Arizona. It is anatomically similar to modern frogs. The oldest known caecilian is another Early Jurassic species, Eocaecilia micropodia, the earliest salamander is Beiyanerpeton jianpingensis from the Late Jurassic of northeastern China

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Lissamphibia
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The Lissamphibia are a group of tetrapods that includes all modern amphibians. Lissamphibians consist of three living groups, the Salientia, the Caudata, and the Gymnophiona, a fourth group, the Allocaudata, was moderately successful, spanning 160 million years from the Middle Jurassic to the Early Pliocene, but became extinct 2.5 million years ago. Some writers have argued that the early Permian dissorophoid Gerobatrachus hottoni is a lissamphibian, if it is not, the earliest known lissamphibians are Triadobatrachus and Czatkobatrachus from the Early Triassic. Some, if not all, lissamphibians share the following characteristics, some of these apply to the soft body parts, hence do not appear in fossils. Nevertheless, Haeckel considered the caecilians to be related to what he called Lissamphibia. In the early to mid 20th century, an origin of amphibians was favoured. With the single origin of amphibians being accepted by most herpetologists and paleontologists, however, the origin and relationships of the various lissamphibian groups both with each other and among other early tetrapods remains controversial. Not all paleontologists today are convinced that Lissamphibia is indeed a natural group, one of the hypotheses regarding their ancestors is that they evolved by paedomorphosis and miniaturization from early tetrapods. Benton, M. J. Vertebrate Palaeontology, 3rd ed. Blackwell, carroll, R. L. Vertebrate Paleontology and Evolution, WH Freeman & Co. San Mauro, Diego, Miguel Vences, Marina Alcobendas, Rafael Zardoya, initial diversification of living amphibians predated the breakup of Pangaea. Biology 356 - Major Features of Vertebrate Evolution by Dr. Robert Reisz, University of Toronto

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Batrachia
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The Batrachia are a clade of amphibians that includes frogs and salamanders, as well as the extinct allocaudates, but not caecilians. The earliest batrachians are the stem-frogs Triadobatrachus and Czatkobatrachus from the Early Triassic, however, several molecular clock estimates place the first appearance of the Batrachia before the Early Triassic. Most estimates place the divergence in the Permian but some put it as far back as 367 million years ago in the Late Devonian, however, there is no evidence of lissamphibians or lissamphibian-like animals in the fossil record at this time. The tetrapod groups that are hypothesized as ancestors of modern amphibians appear in the Late Carboniferous, roughly 300 million years ago

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Salientia
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The oldest fossil proto-frog appeared in the early Triassic of Madagascar, but molecular clock dating suggests their origins may extend further back to the Permian,265 million years ago. Very few fossils of early salientians have been found, which makes defining the characteristics of the group, the early proto-frogs developed from temnospondylid ancestors in which some of the elements of their vertebrae remained separate. The structure of the pelvis and hind limb was probably developed for swimming rather than jumping. From the structure of the vertebrae, the group not to be monophyletic. The evolution of salientians seems to have rapid and radiative. The essential features of recent groupings seem to have been established during the Mesozoic or early Tertiary, the origins and evolutionary relationships between the three main groups of amphibians are hotly debated. This would help account for the scarcity of amphibian fossils from the period before the groups split. The neobatrachians seemed to have originated in Africa/India, the salamanders in East Asia, other researchers, while agreeing with the main thrust of this study, questioned the choice of calibration points used to synchronise the data. They proposed that the date of lissamphibian diversification be put in the Permian, rather less than 300 million years ago, the study postulated the Lissamphibia originated no earlier than the late Carboniferous, some 290 to 305 million years ago. The split between Anura and Caudata was estimated as taking place 292 million years ago, rather later than most molecular studies suggest, in 2008, Gerobatrachus hottoni, a temnospondyl with many frog- and salamander-like characteristics, was discovered in Texas. However, others have suggested that Gerobatrachus hottoni was only a dissorophoid temnospondyl unrelated to extant amphibians, the skull of Triadobatrachus is frog-like, being broad with large eye sockets, but the fossil has features diverging from modern frogs. These include a body with more vertebrae. The tail has separate vertebrae, unlike the fused urostyle or coccyx found in modern frogs, the tibia and fibula bones are also separate, making it probable that Triadobatrachus was not an efficient leaper. The Salientia are a group including modern frogs in the order Anura. The earliest salientian yet discovered is Triadobatrachus massinoti, known from a fossil specimen found in Madagascar. It dates back to the Early Triassic, about 250 million years ago and it had many frog-like features, but had 14 presacral vertebrae, while modern frogs have nine or 10. Previous fossil amphibians had many more vertebrae than this and T. massinoti provides a missing link between salamanders and frogs. Czatkobatrachus is another proto-frog with some similar to Triadobatrachus

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Frog
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A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura. The oldest fossil proto-frog appeared in the early Triassic of Madagascar, Frogs are widely distributed, ranging from the tropics to subarctic regions, but the greatest concentration of species diversity is in tropical rainforests. There are approximately 4,800 recorded species, accounting for over 85% of extant amphibian species and they are also one of the five most diverse vertebrate orders. The body plan of a frog is generally characterized by a stout body, protruding eyes, cleft tongue, limbs folded underneath. Besides living in water and on dry land, the adults of some species are adapted for living underground or in trees. The skin of the frog is glandular, with secretions ranging from distasteful to toxic, Frogs skins vary in colour from well-camouflaged dappled brown, grey and green to vivid patterns of bright red or yellow and black to advertise toxicity and warn off predators. Frogs typically lay their eggs in water, the eggs hatch into aquatic larvae called tadpoles that have tails and internal gills. They have highly specialized rasping mouth parts suitable for herbivorous, omnivorous or planktivorous diets, the life cycle is completed when they metamorphose into adults. A few species deposit eggs on land or bypass the tadpole stage, adult frogs generally have a carnivorous diet consisting of small invertebrates, but omnivorous species exist and a few feed on fruit. Frogs are extremely efficient at converting what they eat into body mass and they are an important food source for predators and part of the food web dynamics of many of the worlds ecosystems. The skin is semi-permeable, making them susceptible to dehydration, so they live in moist places or have special adaptations to deal with dry habitats. Frogs are valued as food by humans and also have many roles in literature, symbolism. Frog populations have declined significantly since the 1950s, more than one third of species are considered to be threatened with extinction and over one hundred and twenty are believed to have become extinct since the 1980s. The number of malformations among frogs is on the rise and a fungal disease. Conservation biologists are working to understand the causes of these problems, the name frog derives from Old English frogga, abbreviated to frox, forsc, and frosc, probably deriving from Proto-Indo-European preu = to jump. About 88% of amphibian species are classified in the order Anura and these include around 4,810 species in 33 families, of which the Leptodactylidae, Hylidae and Ranidae are the richest in species. The use of the common frog and toad has no taxonomic justification. From a classification perspective, all members of the order Anura are frogs, there are numerous exceptions to this rule

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Neobatrachia
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The Neobatrachia are a suborder of the Anura, the order of frogs and toads. This suborder is the most advanced and apomorphic of the three anuran orders alive today, hence its name, which means new frogs. It is also by far the largest of the three, its more than 5,000 different species make up over 96% of all living anurans. Neobatrachia are usually sorted into five superfamilies, but this division is also controversial, in addition, several families have been revealed to be paraphyletic and consequently split up to make them correspond to clades and thus be natural, evolutionary groups. This has approximately doubled the number of presently recognized neobatrachian families, mitochondrial phylogeny of Anura, A case study of congruent phylogenetic reconstruction using amino acid and nucleotide characters. Hoegg, Simone, Miguel Vences, Henner Brinkmann, Axel Meyer, phylogeny and comparative substitution rates of frogs inferred from sequences of three nuclear genes. San Mauro, Diego, Miguel Vences, Marina Alcobendas, Rafael Zardoya, initial diversification of living amphibians predated the breakup of Pangaea

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True toad
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A true toad is any member of the family Bufonidae, in the order Anura. This is the family of anurans in which all members are known as toads. The bufonids now comprise more than 35 genera, Bufo being the most widespread, true toads are widespread and are native to every continent except Australia and Antarctica, inhabiting a variety of environments, from arid areas to rainforest. Most lay eggs in paired strings that hatch into tadpoles, although, in the genus Nectophrynoides, true toads are toothless and generally warty in appearance. They have a pair of glands on the back of their heads. These glands contain a poison which the toads excrete when stressed. The poison in the glands contains a number of toxins causing different effects, different animals contain significantly different substances and proportions of substances. Some, like the cane toad Rhinella marina, are more toxic than others, some psychoactive toads, such as the Colorado River toad Bufo alvaris, have been used recreationally for the effects of their bufotoxin. Male toads possess a Bidders organ, under the right conditions, the organ becomes an active ovary and the toad, in effect, becomes female. The family Bufonidae contains about 500 species among 38 genera, Amphibian Species of the World 5.1 - Bufonidae. Halliday, Tim R. and Kraig Adler, the New Encyclopedia of Reptiles & Amphibians. Facts on File, New York,2002, tolweb. org, Bufonidae Bufonidae. com Amphibian and Reptiles of Peninsular Malaysia - Family Bufonidae FED. us Bufonidae recordings from the British Library Sound Archive

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Incilius
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Incilius is genus of toads in the true toad family, Bufonidae. They are sometimes known as the Central American toads or Middle American toads and are found in southern USA, Mexico, Central America, taxonomy and systematics of Incilius has seen many recent changes. Current delineation of the genus was achieved by 2011 when both Cranopsis/Ollotis and Crepidius/Crepidophryne had been brought into synonymy with Incilius, however, the monophyly of Incilius is threatened by Incilius bocourti, which might be the sister taxon of Anaxyrus. Another discussion has been the level at which the genus is recognized. However, others have argued that Incilius should be treated as a subgenus of Bufo, there are at present 40 species